Good luck with that.
I will tell you my story how I got lumbered with a 2 year contract at o2.
I made an Internet contract when I moved, I was supposed to be connected on a specific date, guess what? I wasn't and I really needed Internet as I work from home. I called maybe 20 times, sent emails etc, they simply ignored my requests and emails afterwhich they told me it's too late to cancel even though I still didn't have Internet 2 weeks after the connection date... I managed to make a contract with a different provider which connected me quickly and been with them ever since.
With O2, I couldn't do anything and had to pay for the contract for Internet that didn't even work for about a month... then when I cancelled the contract they were begging me to stay with them and asked me why would I want to cancel? Ahmmm maybe because you never connected me on the date you were supposed to connect me? Maybe because customer service was extremely bad? Maybe because I paid for 2 years for Internet I didn't use?
But this sales team is very pushy and kept throwing me offers like there's no tomorrow... still, no thank you. Most likely, you'll have to pay, sadly... they have their ways.... telling you it's your fault.
